20 
EXPERIMENTS WITH POTATOES. 
dependence could be placed upon them. Compare J. J. 
Pohl, Watt’s Dictionary of Chemistry, article Potatoes, 
also Biedermann Chemiker, Kalender, the table of 
Behren’s Marker, und Morgen : 
Watt’s Dictionary. Biedermann’s. Found. 
Sp. gr. Starch. Starch. Starch. 
1.094 17.52 16.90 17.75 
The most complete table is that of Heideprien, (Jour. 
Chem. Soc., vol. xxxii.-233). 
Parke’s Hygiene, 6th edition, p. 260, states that when 
potatoes have a specific gravity below 1.068, the quality is 
very bad; between 1.068 and 1.082, inferior ; between 
1.082 and 1.105, rather poor; above 1,105, good. 
Fifth —Two experiments were tried comparing sul¬ 
phuric with hydrochloric acid, all other conditions re¬ 
maining the same : 
Time. Sulphuric acid. Hydrochloric acid. 
3 hours_17.50_17.76 
6 hours_17.46_17.71 
Besides the per cent, of starch being less with sul¬ 
phuric acid, the dark color on prolonged heating is decid¬ 
edly against its use. 
Sixth —Five kilograms (11 lbs.) of potatoes were grated 
and pulverized in a mortar and the starch washed out 
through a linen towel, to see what per cent, of starch 
could be obtained by this method. 
Starch washed out. Starch by Saehsse’s method. 
16.84 per cent. 17.75 per cent. 
The above was washed twenty-four times with water 
and the process extended over a period of two days. 
Seventh —Allihn’s method w T as tried, which in sub¬ 
stance, consists in reducing the sub-oxide of copper to the 
metallic form by heating it to redness in a stream of hy¬ 
drogen, to prevent oxidation. From Allihn’s table, the 
weight of dextrose corresponding to the w T eight of copper 
was found : 
Allihn’s method. 
17.79 per cent. 
Sachsse’s method. 
17.75 per cent. 
